Guess the Pest! Week #25 Answer: Brown Stem Rot of Soybean

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Congratulations to Jacob Urian for correctly identifying the disease as brown stem rot and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle.

Guess the Pest Week #25 Answer: Brown Stem Rot of Soybean
By Nancy Gregory, Plant Diagnostician; ngregory@udel.edu

Brown stem rot of soybean is caused by the fungus Cadophora. Brown stem rot symptoms on stems include a general browning that extends from the soil line up the stem, or starts at a node. Symptoms usually show up in mid-summer/pod fill. When affected stems are split lengthwise, there is a brown discoloration of the vascular tissue. Remnants of the pith made be observed in a ladder like pattern. Foliar symptoms look like sudden death syndrome but Fusarium would be found on basal stems with SDS. Symptoms for both diseases tend to be more severe in fields with soybean cyst nematode.

The BSR fungus survives in soybean residue in the soil, but not on seed, and infects roots early in the season during wet, cool conditions. Univ of Wisconsin researchers have shown that a pH lower than 6.5 favors the development of BSR. Management of brown stem rot includes crop rotation, good residue decomposition and selection of resistant varieties. Some resistance is available to BSR and to SCN. Seed treatments and fungicides do not control brown stem rot.

This was the last Guess the Pest challenge for the 2018 growing season.

Thanks to all that followed along each week and submitted answers. Next week, we will hold the “end of season” raffle for the $100 gift card. Everyone that submitted a correct answer will automatically be entered into the raffle for each correct answer that was submitted. If you were a weekly winner, you will have your name entered not once but five times into the end of season raffle. I will also be contacting you soon to make arrangements to get you a copy of A Farmer’s Guide to Corn Diseases.

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